1. FIELD OF THE INVENTION
The present invention relates to a solid-electrolyte fuel cell system. More particularly, the invention relates to a solid-electrolyte fuel cell system comprising a plurality of fuel cells each having an electrolyte layer, an oxygen electrode applied to one surface of the electrolyte layer, a fuel electrode applied to the other surface of the electrolyte layer, an oxygen-containing gas passage opposed to the oxygen electrode, and a fuel gas passage opposed to the fuel electrode, the fuel cells being stacked to form a cell assembly an oxygen-containing gas supply passage disposed peripherally of the cell assembly, as seen in a stacking direction of the fuel cells, to communicate with the oxygen-containing gas passage; and a fuel gas supply passage disposed peripherally of the cell assembly and separately from the oxygen-containing gas supply passage.
2. DESCRIPTION OF THE RELATED ART
In the conventional solid-electrolyte fuel cell system noted above, an oxygen-containing as exhausted from the oxygen-containing gas passages and a fuel gas exhausted from the fuel gas passages are burnt to produce heat for preheating an oxygen-containing gas to be supplied to the oxygen-containing gas passages. The cell assembly is maintained at a temperature enabling reformation of fuel gas stock into a fuel gas in the cells. Thus, the exhaust oxygen-containing gas and exhaust fuel gas are burnt in a location as close to the cell assembly as possible.
FIG. 28 shows such a solid-electrolyte fuel cell system known in the art. The system includes an oxygen-containing gas supply passage SI disposed in one peripheral position of a cell assembly NC as seen in a stacking direction thereof. This supply passage SI communicates with each oxygen-containing gas passage "s". An oxygen-containing gas exhaust passage SO is disposed in a peripheral position of the cell assembly NC opposite from the supply passage SI to withdraw the oxygen-containing gas from each oxygen-containing gas passage "s". A fuel gas supply passage FI is disposed in a different peripheral position of the cell assembly NC as seen in the stacking direction thereof. This supply passage FI communicates with each fuel gas passage "f". A fuel gas exhaust passage FO is disposed in a peripheral position of the cell assembly NC opposite from the fuel gas supply passage FI to withdraw the fuel gas from each fuel gas passage "f". The system further includes a combustion chamber KI spaced from the cell assembly NC to burn the oxygen-containing gas exhausted from the oxygen-containing gas passages "s" and the fuel gas exhausted from the fuel gas passages "f". The oxygen-containing gas is delivered from the oxygen-containing gas exhaust passage SO to the combustion chamber KI through exhaust oxygen-containing gas passages 21, while the fuel gas is delivered from the fuel gas exhaust passage FO to the combustion chamber KI through exhaust fuel gas passages 22.
The above solid-electrolyte fuel cell system has a disadvantage of complicated construction in that the oxygen-containing gas exhaust passage SO, fuel gas exhaust passage FO, exhaust oxygen-containing gas passages 21 and exhaust fuel gas passages 22 are required in addition to the oxygen-containing gas supply passage SI and fuel gas supply passage FI. Further, heat is radiated from the oxygen-containing gas exhaust passage SO, fuel gas exhaust passage FO, exhaust oxygen-containing gas passages 21 and exhaust fuel gas passages 22. The combustion chamber KI, which is spaced from the cell assembly NC, provides a low heating efficiency and releases a large amount of heat. Thus, the known system as a whole suffers a great heat loss.
The known system includes the oxygen-containing gas supply passage SI, fuel gas supply passage FI, oxygen-containing gas exhaust passage SO and fuel gas exhaust passage FO arranged peripherally of the cell assembly NC. Even though the combustion chamber KI also is disposed peripherally of the cell assembly NC, only a small space is available around the cell assembly NC for installing the combustion chamber KI. A minimal area is allowed for contact between the cell assembly NC and combustion chamber KI, which results in low heating efficiency and a large amount of heat radiation from the combustion chamber KI.